Ovulation is the process that happens usually once in every menstrual cycle. In ovulation the ovary releases one (rarely more) egg. Usually hormone changes in female body triggers the ovulation.
Ovulation happens usually once in every menstrual cycle. You can only become pregnant if a sperm fertilises at least one egg. Ovulation usually happens 12 to 16 days before your next period starts.
The eggs are contained in your ovaries. During the first part of each menstrual cycle, one of the eggs is being grown and matured.
- As you approach ovulation, your body produces increasing amounts of a hormone called estrogen, which causes the lining of your uterus to thicken and helps create a sperm friendly environment.
- These high estrogen levels trigger a sudden increase in another hormone called luteinising hormone (LH). The ‘LH’ surge causes the release of the mature egg from the ovary – this is ovulation.
- Ovulation normally occurs 24 to 36 hours after the LH surge, which is why the LH surge is a good predictor of peak fertility.
- The egg can only be fertilised for up to 24 hours after ovulation. If it isn’t fertilised the lining of the womb is shed (the egg is lost with it) and your period begins. This marks the start of the next menstrual cycle.
Ovulation and fertile days
While an egg only survives for up to 24 hours, sperm can remain active for up to five days. It may therefore be surprising to learn that a couple can conceive through sexual intercourse four to five days before the egg is released.
The total ‘fertility window’, taking into account the lifetime of both the sperm and the egg, is about six days. The ‘fertile days’ are all the days during your menstrual cycle when you have the ability to become pregnant if you have unprotected sex.
Identification of additional fertile days provides couples with more flexibility to plan intercourse around their lifestyle and also more opportunities to conceive, which may reduce the pressure that couples can experience when trying to get pregnant.
The days during each cycle when you are most fertile, and therefore most likely to get pregnant from unprotected sex, are the day of ovulation and the day before – these are the two days of peak fertility. There are also a few days before this when you experience high fertility and also have an opportunity to get pregnant. Outside this ‘fertility window’ of about six days, the chances of getting pregnant are low.
Menstrual cycle length varies from woman to woman and from cycle to cycle but is typically between 23 and 35 days. Ovulation usually happens 12-16 days before the next period. Many women think that they ovulate on day 14 but this is just an average. Most women will actually ovulate on a different day of the menstrual cycle, and this will also vary from cycle to cycle. In fact, 46% of menstrual cycles vary by seven or more days.
Some women claim to feel a twinge of pain when they ovulate, but many feel no sensation at all and there are no other physical signs of ovulation. To get pregnant, it’s important to have intercourse on your fertile days; if you want to find out when are your most fertile days, it’s important to get to know your own body and your own personal menstrual cycle.
As ovulation is the release of an egg from an ovary it’s almost instantaneous – the follicle bursts and the egg is propelled very quickly into the Fallopian tube.